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 Those numbers are based on air traffic remaining at full capacity.
Assuming an 80 percent reduction in travel to reflect that many
airlines are halting flights to affected regions, France's risk is
still 25 percent, and Britain's is 15 percent.
"It's really a lottery," said Derek Gatherer of Britain's Lancaster
University, an expert in viruses who has been tracking the epidemic
- the worst Ebola outbreak in history.
The deadly epidemic has killed more than 3,400 people since it began
in West Africa in March and has now started to spread faster,
infecting almost 7,200 people so far. Nigeria, Senegal and now the
United States - where the first case was diagnosed on Tuesday in a
man who flew in from Liberia - have all seen people carrying the
Ebola hemorrhagic fever virus, apparently unwittingly, arrive on
their shores.
France is among countries most likely to be hit next because the
worst affected countries include Guinea, alongside Sierra Leone and
Liberia, which is a French-speaking country and has busy travel
links back, while Britain's Heathrow airport is one of the world's
biggest travel hubs.
France and Britain have each treated one national who was brought
home with the disease and then cured. The scientists' study suggests
that more may bring it to Europe not knowing they are infected.
"If this thing continues to rage on in West Africa and indeed gets
worse, as some people have predicted, then it's only a matter of
time before one of these cases ends up on a plane to Europe," said
Gatherer.
Belgium has a 40 percent chance of seeing the disease arrive on its
territory, while Spain and Switzerland have lower risks of 14
percent each, according to the study first published in the journal
PLoS Current Outbreaks and now being regularly updated at http://www.mobs-lab.org/ebola.html.
The World Health Organization (WHO) has not placed any restrictions
on travel and has encouraged airlines to keep flying to the
worst-hit countries. British Airways and Emirates airlines have
suspended some flights
But the risks change every day the epidemic continues, said Alex
Vespignani, a professor at the Laboratory for the Modeling of
Biological and Socio-Technical Systems at Northeastern University in
Boston who led the research.
"This is not a deterministic list, it's about probabilities - but
those probabilities are growing for everyone," Vespignani said in a
telephone interview. "It's just a matter of who gets lucky and who
gets unlucky."
The latest calculations used data from October 1.
"Air traffic is the driver," Vespignani said. "But there are also
differences in connections with the affected countries (Guinea,
Liberia and Sierra Leone), as well as different numbers of cases in
these three countries - so depending on that, the probability
numbers change."
PATIENTS UNAWARE
Patients are at their most contagious when Ebola is in its terminal
stages, inducing both internal and external bleeding, and profuse
vomiting and diarrhea - all of which contain high concentrations of
infectious virus.
But the disease can also have a long incubation period of up to 21
days, meaning that people can be unaware for weeks that they are
infected, and not feel or display any symptoms.
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This, it seems, is what allowed the Liberian visitor Thomas Eric
Duncanto to fly to the United States and spend several days there
unaware that he was carrying the deadly virus, before being
diagnosed and isolated.
In the European Union, free movement of people means someone
unknowingly infected with Ebola could easily drive through several
neighboring countries before feeling ill and seeking help, and spend
weeks in contact with friends or strangers before becoming sick
enough to show up on airport scanners.
Jonathan Ball, a professor of molecular virology at Britain's
Nottingham University said that even with exit screening at airports
of affected countries, the long, silent incubation period meant
"cases can slip through the net".
"Whilst the risk of imported Ebola virus remains small, it's still a
very real risk, and one that won't go away until this outbreak is
stopped," he said. "Ebola virus isn't just an African problem."
However, the chance of the disease spreading widely or developing
into an epidemic in a wealthy, developed country is extremely low,
healthcare specialists say.
According to the latest Ebola risk assessment from the European
Centers of Disease Prevention and Control, which monitors health and
disease in the region, "the capacity to detect and confirm cases...
is considered to be sufficient to interrupt any possible local
transmission of the disease early."
Gatherer cited Nigeria as an example of how Ebola can be halted with
swift and detailed action.
Despite being in West Africa and being home to one of the world's
most crowded, chaotic cities, Nigeria has managed to contain Ebola's
spread to a total of 20 cases and 8 deaths, and looks likely to be
declared free of the virus in coming weeks.
"Even if we have a worse case scenario where someone doesn't present
for medical treatment, or... it's not correctly identified as Ebola,
and we get secondary transmission, it's not likely to be a very long
secondary transmission chain," he said.
"People aren't living in very crowded conditions (in Europe), so the
disease doesn't have the same environment it has in a shanty town in
Monrovia, where the environment is perfect for it to spread. It's a
different matter in modern western cities with the very sanitized,
sterile lives that we live."
(Refiled to clarify paragraph five)
(Editing by Sophie Walker)
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